Magnetic plunger switches are well known in the industry, even for use as a sensor for sensing the presence of a movable object such as a door or window. Such an example is found in Huckins et al., U.S. Pat. No. 5,155,460 B1, issued in reexamination on May 16, 2005 and entitled “Switch Housing with Magnetic Roller Plunger.” However, the Huckins invention is still hard wired and not sufficiently compact to be installed after-market into windows and doors without voiding the window or door manufacturer's warranty.
Other magnetic plunger switches exist even for the recessed market, but all in the “wired” version, such (i) GE Recessed Roller Plunger with wire leads 3005 [1.5″ long×0.75″ diam.], (ii) Honeywell Mini roller Contact Plunger with Terminals 956RPT [1.47″ long×0.75″ diam.], (iii) AMSECO Rollerball Switch RSW-21 Series [1.68″ long×0.71″ diam], and (iv) George Risk Industries Short Roller Ball Switch DS-01 Series [1.31″ long×0.73″ diam.]). These “wired” designs have an advantage over earlier recessed switches in that an external magnet is not required to be setup, aligned, adjust, biased or hidden.
But if wireless signal transmission is desired, the length of the current recessed plunger switches are even larger than these wired switches as shown in examples such as the Honeywell 5818MNL Recessed Door/Window Transmitter (3.00″ long by 0.75″ diameter) or DSC EV-DW319 Recessed Door/Window Sensor (2.50″ long×0.75″ diameter). No compact wireless sensor with a plunger style switch was known to exist.